The magnetic disk device, includes an actuator for positioning the head attached to the tip at a target position on the disk. In the magnetic disk device, the skew angle of the head with respect to the circumferential direction of the disk usually changes within a particular angle range. In order to improve the random access performance, a magnetic disk device having an actuator shorter (hereinafter referred to as a short actuator) than a normal actuator is studied. The range of the skew angle of the head by the short actuator is larger than the range of the skew angle of the head by the normal actuator. Therefore, in a magnetic disk device provided with a short actuator, a recording region of a disk is divided into a where the recording quality of data can be ensured and a region where the recording quality of data can not be ensured.